This invention relates, in general, to optical switches, and more particularly to an integrated optical switch which senses ambient lighting and couples or decouples a load from a voltage source.
For example, ambient light sensed by an optical sensor triggers circuitry which couples a load to a voltage source when light falls below a preset threshold. A common application for this type of optical switch is to turn a light bulb on or off depending on ambient lighting conditions. The voltage source which is coupled to the load through the optical switch is 120 VAC.
Design factors for this type of optical switch are very simple. First, the optical switch must be able to handle the power requirements of the load. Second, specifications for the optical sensor are not extremely critical. Finally, the overriding factor in the design of the optical switch pertain to cost, manufacturability, and the simplicity in which it can be integrated in a lighting system.
Previous methods for building a cost effective optical switch involved discrete components. Typically, a discrete SCR is used to couple a light source (or load) to a voltage source, a discrete optical sensor (for example, a CdS photo resistor) monitors ambient light conditions and will change resistance based on the light it receives, the optical sensor in combination with a resistor are used as a control element for enabling or disabling the SCR. From a manufacturing standpoint, the individual components must be purchased separately, assembled on a breadboard, and the breadboard integrated into the lighting system. Building the optical switch from discrete components increases costs, increases assembly time, is more prone to manufacturing errors (due to the number of components which must be handled), and uses space inefficiently.
It would be of great value if an integrated optical switch were available which reduces size, reduces cost, and eliminates the need for assembling a switch from discrete components.